\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, scale=0.8,european]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw (0,0) to [pR,name=pr] (5,0) to [cute open switch] (6,0)--(7,0) ;      
  \draw (0,0)--(0,-1.5);
  \draw (7,0)--(7,-1.5);
  \draw [fill=white](0,-1.5) circle (2pt);
  \draw [fill=white](7,-1.5) circle (2pt);
  \draw [fill=black](0,0) circle (2pt);
  \draw (0,0) -- (0,1) to [R=$R$] (0,1-|pr.wiper)--(pr.wiper); 
  \node at (pr.left) [below left]{$A$};
  \node at (pr.right)[below right]{$B$};
  \node at (5.5,-.4){$K$};
  \draw [<->](0+.1,-1.5)-- (7-.1,-1.5)node [midway,above]{$U$};
\end{circuitikz}
\end{document}